1. Field of the Invention
The present invention relates to an organic light emitting display device (OLED) and a method of manufacturing the same, and more particularly, to an OLED and a method of manufacturing the same, which can prevent galvanic corrosion and deterioration of adhesion between a first electrode and the source and drain electrodes during rework of the first electrode.
2. Description of the Related Art
Generally, an organic light emitting display device (OLED) is a self-emissive display device which emits light by exciting fluorescent organic compounds. The OLED may be classified as either a passive matrix (PM) type and an active matrix (AM) type, depending upon how and N×M number of unit pixels that are arranged in a matrix shape are driven to emit light. In comparison to the PM type, the AM type is adequate for large-area devices due to its low power consumption and its high resolution.
OLEDs may also be divided into a top-emitting OLED, a bottom-emitting OLED, and a double-sided emitting OLED, depending upon the direction in which light is emitted from organic compounds incorporated into the OLED. Unlike the bottom-emitting OLED, the top-emitting OLED emits light in a direction extending opposite to a substrate on which pixels are arranged; the top-emitting OLED has an advantage of a high aperture ratio.
In the top-emitting OLED, a first electrode may be formed of a conductive material with excellent reflective characteristics and an appropriate work function. It is difficult however, to find an electrically conductive material that satisfies all of the above-described requirements. To solve this problem, the first electrode of a top-emitting OLED may include a reflective layer for reflecting light.
A typical OLED may be constructed with an interlayer insulating layer formed on the entire surface of a substrate bearing a gate electrode, and the interlayer insulating layer is etched to expose a predetermined region of the semiconductor layer through contact holes. A material is deposited on the entire surface of the substrate and is patterned to form source and drain electrodes which are connected to region of the semiconductor layer. A planarization layer is formed on the entire surface of the substrate and is etched to form a via hole which exposes any one of the source and drain electrodes. A reflective layer and a first electrode are formed on the planarization layer and are connected to one of the source and drain electrodes.
If inspection reveals either the reflective layer or the first electrode to be incompletely formed, the reflective layer or the first electrode must be removed and formed again using a rework process. During the removal however, when the source and drain electrodes and the reflective layer which is in contact with the source and drain electrodes are simultaneously exposed to an etchant. The source and drain electrodes have a low electromotive force (EMF) and lose electrons at higher rate than does the reflective layer, which has a higher EMF; thus, the source and drain electrodes are etched at higher rate than is the reflective layer. The EMF in the instant application is measured against a standard hydrogen reference electrode. The EMF may be alternatively named as the standard electrode potential. Owing to its high EMF, the reflective layer will attract electrons while re-depositing the etchant on the reflective layer. As the rate of etching of the reflective layer slows down, galvanic corrosion occurs. As a result, the rework process is difficult, and adhesion between the source and drain electrodes, and the first electrode and the reflective layer deteriorates, thereby causing a concomitant increase in contact resistance between the source and drain electrodes, and the first electrode and the reflective layer.